Physiology Flashcards
(74 cards)
osmolarity is… and how do you calculate it?
no of osmotically active particles in solution
no of particles x molar concentration
osmolarity of body is
300mmol/l
tonicity is…
effect solution has on cell- hypo (inc cell size), hyper (dec cell size), isotonic (normal)
what are the 2 components that make up total body water
ECF- interstitial fluid (80%), plasma, lymph
ICF
what are some tracers used to measure vol distribution and how to measure?
TBW- 3H2O, ECF- inulin, plasma- labelled albumin
unknown V= dose/ sample [ ]
T/F: ICF has more Na+
F: ECF- more Na+, Cl- and HCO3-. ICF- more K+
what is electrolyte balance important?
- total electrolyte [ ] can directly affect water balance
- [ ] of individual electrolytes can affect cell function
(e.g. small changes in K+ may result in cardiac arrest, small changes in Na+ may results in inc BP)
name some functions of the kidneys
water balance, salt balance, plasma vol & osmolarity maintenance, acid-base balance, metabolic waste excretion, renin & erythropoietin secretion, vitD to calcitriol conversion
name the functional unit of the kidney, what it does, and its blood supply
the nephron- filters, reabsorbs and secretes (from capillaries > tubules and vice versa).
BS: artery > afferent artery > glomerulus > efferent arteriole > peritubular capillaries > vein
T/F: not all of the nephron is found in the medulla
T: only loop of henle and collecting duct found in medulla
what is the difference between juxtamedullary and cortical nephrons
juxtamedullary has much longer loop of hele
what is the juxtamedullary apparatus
region where efferent and afferent arterioles bifurcate. contains the granular cells (secrete renin) and the macula densa which detects salt levels in tubule fluid- main regulators of downstream blood flow through capillaries
what are the methods of filtering blood
glomerular filtration (occurs in glomeruli in bowman’s capsule), tubular reabsorption and tubular secretion
know how to calculate rate of filtration and rate of excretion, as well as rate of reabsorption and rate of secretion.
what is an important golden rule when it comes to net reabsorption and net sceretion
if rate of filtration > rate of excretion= net reabsorption has taken place
if rate of excretion> rate of filtration= net secretion has occurred
how much plasma is filtered in glomerulus
20%
what are the 3 barriers proposed by glomerular membrane that block filtration
glomerular capillary endothelium, basement membrane, slit processes of podocytes
there are 4 forces that allow for net filtration pressure (driving force of plasma across glomerular membrane)- 2 oppose and 2 drive, these are?
favouring: glomerular capillary BP, bowman’s capsule oncotic pressure
oppsoing: bowman’s capsule hydrostatic pressure, capillary oncotic pressure
how to calculate net filtration pressure
net filtration= add up forces favouring filtration - forces opposing filtration
GFR is… and how to calculate
rate at which protein-free plasma is filtered from glomeruli into BC per unit time
GFR = Kf x net filtration pressure
normal GFR= 125ml/min
2 regulators of blood flow and GFR
extrinsic: sympathetic control via baroreceptor reflex- constriction of afferent arteriole
intrinsic:
- myogenic mechanism: if vascular SM is stretched it contracts thus constricting arteriole
- tubuloglomerular feedback system: ^ GFR= macula densa detects inc NaCl so releases vasoactive chemicals, SM contraction of afferent arteriole
what may have affects on GFR
anything affecting glomerular capillary BP, bowman’s capsule oncotinc pressure, bowman’s hydrostatic pressure, glomerular capillary oncotic pressure
e.g. diarrhoea inc oncotic pressure of glomerular capillary so dec GFR
what is key to markers
should be filtered but not secreted or reabsorbed
how to measure clearance of substance
clearance of X=( [X] in urine x Vurine ) / [X] plasma
ANS= ml/min
what are 2 main clearance markers (GFR markers)
inulin (exogenous so hard to administrate), creatinine (slightly secreted so close approx for GFR)
